Table Of ContentHardware/General
Make: PROJECTS M Make: PROJECTS
Making Things Talk
a
k
e
Making
:
P
R Practical
Building electronic projects that interact with the physical world is good fun. O
J Methods for
E
But when devices that you’ve built start to talk to each other, things really start C
T Connecting
S
to get interesting. Making Things Talk demonstrates that once you fi gure out
Things Talk Physical Objects
how objects communicate — whether they’re microcontroller-powered devices,
M
email programs, or networked databases — you can get them to interact.
a
k
Microcontrollers, personal computers,
You will:
and web servers talking to each other. i PROJECTS
n
» Make your pet’s bed send you email. Tom Igoe AND IDEAS
g
This book is perfect for people with little technical
TO CREATE
training but a lot of interest. Maybe you’re a science » Make your own game controllers that T
TALKING
teacher who wants to show students how to communicate over a network.
h
monitor weather conditions at several locations at OBJECTS FROM
» i
once, or a sculptor who wants to stage a room of Use ZigBee, Bluetooth, Infrared, and plain n ANYTHING
choreographed mechanical sculptures. old radio to transmit sensor data wirelessly.
g
Whether you need to plug some sensors in your home » Work with three easy-to-program, open s
to the Internet or create a device that can interact source environments: Arduino/Wiring, T
wirelessly with other creations, Making Things Talk Processing, and PHP.
a
explains exactly what you need.
l
» Write programs to send data across the k
Internet based on physical activity in your
Through twenty-six simple projects, Making Things
home, offi ce, or backyard.
Talk shows how to get your creations to talk with
one another by forming networks of smart devices
that carry on conversations with you and your
Tom Igoe teaches courses in physical computing and networking at the
environment. Here are just a few of the projects:
Interactive Telecommunications Program in the Tisch School of the Arts at
New York University. In his teaching and research, he explores ways to allow
Blink XBee Toxic Sensor
digital technologies to sense and respond to a wider range of human physical
Your very fi rst program. Use ZigBee, sensors, expression. He co-authored Physical Computing: Sensing and Controlling the
Monski pong and a cymbal monkey to Physical World with Computers with Dan O’Sullivan, which has been adopted
warn of toxic vapors. by numerous digital art and design schools around the world. He is a contributor
Control a video game
to MAKE magazine and a collaborator on the Arduino open source micro-
with a fl uffy pink Bluetooth GPS T
controller project. He hopes someday to work with monkeys, as well.
monkey. Build a battery-powered o
m
GPS that reports its
Networked Air Quality location over Bluetooth. I
Meter g
Download and display RFID Reader Bowl o
e
the latest report for your Turn your lights off
city. when you leave the
home or offi ce.
US $29.99 CAN $35.99 www.oreilly.com
y(7IA5J6*PLKPLK( +,!?!;!;!} ISBN–10: 0-596-51051-9
ISBN–13: 978-0-596-51051-0
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Making
Things Talk
First Edition
Tom Igoe
BEIJING • CAMBRIDGE • FARNHAM • KÖLN • PARIS • SEBASTOPOL • TAIPEI • TOKYO
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Making Things Talk
by Tom Igoe
Copyright © 2007 O’Reilly Media, Inc. All rights reserved. Printed in U.S.A.
Published by Make:Books, an imprint of Maker Media, a division of O’Reilly Media, Inc.
1005 Gravenstein Highway North, Sebastopol, CA 95472.
O’Reilly books may be purchased for educational, business, or sales promotional use.
For more information, contact our corporate/institutional sales department:
800-998-9938 or [email protected].
Print History Publisher: Dale Dougherty
September 2007 Associate Publisher and Executive Editor: Dan Woods
First Edition Editor: Brian Jepson
Copy Editor: Nancy Kotary
Creative Director: Daniel Carter
Designer: Katie Wilson
Production Manager: Terry Bronson
Indexer: Patti Schiendelman
Cover Photograph: Tom Igoe
The O’Reilly logo is a registered trademark of O’Reilly Media, Inc. The MAKE: Projects series
designations, Making Things Talk, and related trade dress are trademarks of O’Reilly Media, Inc.
Many of the designations used by manufacturers and sellers to distinguish their products are claimed
as trademarks. Where those designations appear in this book, and O’Reilly Media, Inc. was aware of
the trademark claim, the designations have been printed in caps or initial caps.
While every precaution has been taken in the preparation of this book, the publisher and authors
assume no responsibility for errors or omissions, or for damages resulting from the use of the
information contained herein.
Please note: Technology, and the laws and limitations imposed by manufacturers and content owners,
are constantly changing. Thus, some of the projects described may not work, may be inconsistent
with current laws or user agreements, or may damage or adversely affect some equipment.
Your safety is your own responsibility, including proper use of equipment and safety gear, and
determining whether you have adequate skill and experience. Power tools, electricity, and other
resources used for these projects are dangerous unless used properly and with adequate precautions,
including safety gear. Some illustrative photos do not depict safety precautions or equipment, in
order to show the project steps more clearly. These projects are not intended for use by children.
Use of the instructions and suggestions in Making Things Talk is at your own risk. O’Reilly Media, Inc.,
disclaims all responsibility for any resulting damage, injury, or expense. It is your responsibility to
make sure that your activities comply with applicable laws, including copyright.
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ISBN-13: 978-0-596-51051-0
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Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VIII
Who This Book Is For . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X
What You Need To Know . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .XI
Contents of This Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .XI
On Buying Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XII
Using Code Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XIII
Using Circuit Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XIII
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XIV
We’d Like to Hear from You . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .XV
Chapter 1: The Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
It Starts with the Stuff You Touch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
It’s About Pulses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Computers of All Shapes and Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Good Habits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Using the Command Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
It Ends with the Stuff You Touch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Chapter 2: The Simplest Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Layers of Agreement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
Making the Connection: The Lower Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Saying Something: The Application Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Project 1: Monski Pong . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Flow Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Project 2: Wireless Monski Pong . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Project 3: Negotiating in Bluetooth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Chapter 3: A More Complex Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Network Maps and Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Clients, Servers, and Message Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Project 4: A Networked Cat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112
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Chapter 4: Look Ma! No Computer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114
Introducing Network Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Project 5: Hello Internet! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
An Embedded Network Client Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
Project 6: Networked Air Quality Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
Serial-to-Ethernet Modules: Programming and Troubleshooting Tools . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
Chapter 5: Communicating in (Near) Real Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
Interactive Systems and Feedback Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
Transmission Control Protocol: Sockets & Sessions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
Project 7: A Networked Game . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
Chapter 6: Wireless Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Why Isn’t Everything Wireless? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
Two Flavors of Wireless: Infrared and Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
Project 8: Infrared Transmitter-Receiver Pair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
Project 9: Radio Transmitter-Receiver Pair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
Project 10: Duplex Radio Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
An XBee Serial Terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
Project 11: Bluetooth Transceivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
What About Wi-Fi? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
Buying Radios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
Chapter 7: The Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
Look, Ma: No Microcontroller! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .222
Who’s Out There? Broadcast Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .223
Project 12: Reporting Toxic Chemicals in the Shop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .228
Directed Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .246
Project 13: Relaying Solar Cell Data Wirelessly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .250
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .259
Chapter 8: How to Locate (Almost) Anything . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
Network Location and Physical Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .262
Determining Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .265
Project 14: Infrared Distance Ranger Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .266
Project 15: Ultrasonic Distance Ranger Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .268
Project 16: Reading Received Signal Strength Using XBee Radios . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
Project 17: Reading Received Signal Strength Using Bluetooth Radios . . . . . . . . . . . . . . . . . . . . . . . . 276
Determining Position Through Trilateration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277
Project 18: Reading the GPS Serial Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
Determining Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .284
Project 19: Determining Heading Using a Digital Compass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .284
Project 20: Determining Attitude Using an Accelerometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
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Chapter 9: Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
Physical Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .296
Project 21: Color Recognition Using a Webcam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .298
Project 22: 2D Barcode Recognition Using a Webcam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303
Project 23: Reading RFID Tags in Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .308
Project 24: RFID Meets Home Automation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
Network Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .326
Project 25: IP Geocoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .328
Project 26: Email from RFID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .340
Appendix A: And Another Thing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
Other Useful Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .344
Proxies of All Kinds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
Mobile Phone Application Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .352
Other Microcontrollers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .356
New Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .358
Appendix B: Where to Get Stuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360
Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .362
Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .366
Appendix C: Program Listings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419
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VIII MAKING THINGS TALK
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Making Things Talk
MAKE: PROJECTS
Preface
A few years ago, Neil Gershenfeld wrote a smart book called When
Things Start to Think. In it, he discussed a world in which everyday
objects and devices are endowed with computational power: in other
words, today. He talked about the implications of devices that exchange
information about our identities, abilities, and actions. It’s a good read,
but I think he got the title wrong. I would have called it When Things
Start to Gossip. Because let’s face it, even the most exciting thoughts
are worthwhile only once you start to talk to someone else about them.
This is a book about learning to make things that have computational
power talk to each other, and about giving people the ability to use
those things to communicate with each other.
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